From e23fecdc48dc34a61b05296f101bff13fbf9be7d Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Wed, 16 Mar 2022 18:26:12 +0200
Subject: [PATCH] Refactor object prototype discovery in the blender exporter

---
 blender/io_mspgl/scene.py | 47 ++++++++++++++++++++++++++-------------
 1 file changed, 31 insertions(+), 16 deletions(-)

diff --git a/blender/io_mspgl/scene.py b/blender/io_mspgl/scene.py
index 70dbc8c9..7a0fa2f0 100644
--- a/blender/io_mspgl/scene.py
+++ b/blender/io_mspgl/scene.py
@@ -1,3 +1,4 @@
+import itertools
 import mathutils
 
 def is_same_object(obj1, obj2):
@@ -56,29 +57,43 @@ class Scene:
 		if obj_filter:
 			objects = list(filter(obj_filter, objects))
 
-		processed = set()
 		for o in objects:
-			if o.name in processed:
-				continue
-
 			if o.type=='MESH':
-				clones = [c for c in objects if is_same_object(o, c)]
-				self.prototypes.append(o)
-				instance_list = self.instances
-				if o.material_slots and o.material_slots[0].material:
-					mat = o.material_slots[0].material
-					if mat.blend_method=='BLEND':
-						instance_list = self.blended_instances
-					if mat.image_based_lighting:
-						self.use_ibl = True
-				for c in clones:
-					instance_list.append(Instance(c, o))
-					processed.add(c.name)
+				self.add_instance(Instance(o, o))
 			elif o.type=='LIGHT':
 				self.lights.append(o)
 				if o.data.use_shadow:
 					self.use_shadow = True
 
+		proto_map = {}
+		for i in itertools.chain(self.instances, self.blended_instances):
+			p = proto_map.get(i.prototype)
+			if p:
+				i.prototype = p
+			else:
+				found = False
+				for p in proto_map.values():
+					if is_same_object(i.prototype, p):
+						proto_map[i.prototype] = p
+						i.prototype = p
+						found = True
+						break
+
+				if not found:
+					proto_map[i.prototype] = i.prototype
+					self.prototypes.append(i.prototype)
+
+	def add_instance(self, instance):
+		obj = instance.prototype
+		instance_list = self.instances
+		if obj.material_slots and obj.material_slots[0].material:
+			mat = obj.material_slots[0].material
+			if mat.blend_method=='BLEND':
+				instance_list = self.blended_instances
+			if mat.image_based_lighting:
+				self.use_ibl = True
+		instance_list.append(instance)
+
 	def get_chain(self):
 		result = []
 		if self.background_set:
-- 
2.45.2